ci: bring back bare metal OS builds (#105) #293

Job	Run time
cross (powerpc-unknown-linux-gnu, stable)	1m 9s
rustfmt	14s
doc	28s
clippy	27s
test (stable)	41s
cross (powerpc-unknown-linux-gnu, 1.85.0)	1m 11s
no_std (1.85.0, thumbv7em-none-eabi)	40s
no_std (stable, thumbv7em-none-eabi)	44s
test (1.85.0)	37s
no_std (1.85.0, wasm32-unknown-unknown)	41s
no_std (1.85.0, armv7a-none-eabi)	41s
no_std (stable, armv7a-none-eabi)	44s
no_std (stable, wasm32-unknown-unknown)	45s
	9m 2s

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